Collapsible chassis for strollers or baby carriages are known which are substantially constituted by a lower frame, which comprises one or two front posts and one or two rear posts, which support in a downward region respective wheel assemblies, and by at least one upper post, known in the jargon as handle tube, which ends in an upward region with the handle or handgrip of the chassis and can move, with respect to the lower frame, with a rotary motion about a pivoting axis, in order to allow the execution of the closure or compaction of the chassis.
During the transition of the chassis from the extended condition to the collapsed condition, the front post also is rotated about an articulation axis that is parallel to the pivoting axis of the upper post in order to move angularly the upper post toward the rear post, so as to compact the chassis in a longitudinal direction.
This constructive solution allows, during the closure of the chassis, to move the front posts to an angularly closer position with respect to the respective rear posts, while the handle tube, by way of a rotary motion, is arranged, in the closed condition, substantially parallel to the rear posts.
Some of the known solutions provide, for this type of chassis, that the transition from the extended condition to the collapsed condition occurs by rotating the upper post (or handle tube) about the articulation axis and by connecting directly, by way of kinematic connection means, the upper post to the front post so that the rotation of the upper post about its own pivoting axis causes the rotation of the front post with respect to its own articulation axis.
Other solutions instead provide for control means, supported by the lower frame and connected kinematically to the front post in order to rotate it with respect to said lower frame.
In this specific case there are also kinematic connection means between the front post and the handle tube such as to determine, as a consequence of the rotation of the rear post, a consequent rotation of the handle tube.
In all the known solutions that provide for simultaneous movement, during the closing and opening steps, of the front post and of the handle tube there are kinematic connection means that directly connect the front post and the handle tube and are constituted typically by gears, interconnection linkages or equivalent means such as cables or traction elements.
Known solutions, though being widely used, suffer drawbacks.
First of all, in many cases the operations for closing and opening the chassis are scarcely practical and have criticalities in operation.
Furthermore, it is not always easy to manage rotation angles of a different breadth of the handle tube and of the front post.
Finally, sometimes it is difficult to actuate the closure of the chassis by means of lifting handles, it being necessary to provide devices that act by pushing or pulling directly on the posts.